Add the Reversible class.

[dead/harbl.git] / harbl / src / Network / DNS / RBL / Reversible.hs

diff --git a/harbl/src/Network/DNS/RBL/Reversible.hs b/harbl/src/Network/DNS/RBL/Reversible.hs
new file mode 100644 (file)
index 0000000..cbd1529
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+++ b/harbl/src/Network/DNS/RBL/Reversible.hs
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+-- | The 'Reversible' typeclass.
+
+module Network.DNS.RBL.Reversible ( Reversible(..) )
+where
+
+-- | This class is pretty straightforward. It's for things that you
+-- can reverse, or flip around, or make backwards, or however you want
+-- to think of it. Our primary application is to hostname components.
+--
+class Reversible a where
+  backwards :: a -> a